One has to first imagine that a photon isn't as immutable as one sometimes believes. Effectively by putting lots of photons together in a medium (the medium mak

One has to first imagine that a photon isn't as immutable as one sometimes believes. Effectively by putting lots of photons together in a medium (the medium makes sure momentum and energy is conserved) one can create all kinds of colors of light. We can already make "lasers" up to x-rays in synchrotrons by using the right means. The definition of laser becomes a bit shady though as the light is coherent and has a small divergence angle, but is not produced through stimulated emission.